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Swimming
crabs are colourful and active crabs. They are common in the coral
rubble area and seagrass lagoon. Besides the large adults, small juvenile
swimming crabs are also hidden among the seagrass and seaweed, and
other nooks and crannies.
Super Swimmers: Swimming crabs
are among the few crabs that are swift and agile swimmers. They usually
swim sideways, but can also swim backwards and sometimes forwards.
They swim with their paddle-shaped fifth pair of legs. These rotate
like propeller blades when they swim. However, these crabs are essentially
bottom-dwellers and don't swim about all the time. They often hide
among the vegetation and slip under rocks and into other narrow crevices.
Swimming crabs have a streamlined shape for racing through the water.
They have long pincers armed with sharp spines to snag fish and other
fast moving prey. Often, one pincer is slightly larger than the other.
Among the species commonly seen on Chek Jawa are Thalamita
spp. (they have four teeth on the margin of the side of the shell)
and Charybdis spp. (have five teeth).
Fierce Crabs: If disturbed, swimming
crabs often fearlessly wave their pincers menacingly. This is not
an idle threat. If you come too close, this crab might just give a
good pinch that draws blood!
Swimming crab food: They eat fish,
worms, other crustaceans (including other crabs), clams and snails.
They may also nibble on seaweed.
Swimming crab Babies: Like other
crabs, swimming crabs can only mate when the female is moulting. See
the Flower crab fact sheet for details on this.
Human
uses: Swimming crabs are edible and enjoyed by people everywhere.
In the US, the Blue crab (Callinectes sapidus), a member of
the Family Portunidae, is important commercially. In our part of the
world, from Asia to Australia., the Flower crab
(Portunus pelagicus) is one of the commonly eaten member of
this family.
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Orange
swimming crab
Thalamita anisodon
Green
swimming crab
Thalamita sp.
Swimming crabs
can hide in
narrow places
These crabs were
in the middle
of doing something... |
See
also ...
Flower crab (Portunus pelagicus) which is
also a Swimming crab.
Links
Family Portunidae
by Eric De Muylder on the Land Crabs of the Seychelles Islands website:
brief descriptions and photos of Syclla and Thalamita spp.
and other members of the family Portunidae.
Other references
- Tan, Leo W. H.
& Ng, Peter K. L., 1988. A Guide to Seashore Life. The Singapore
Science Centre, Singapore. 160 pp. online
version
- Lim, S., P. Ng,
L. Tan, & W. Y. Chin, 1994. Rhythm of the Sea: The Life and Times
of Labrador Beach. Division of Biology, School of Science, Nanyang
Technological University & Department of Zoology, the National University
of Singapore. 160 pp.
- Chuang, S. H.,
1961. On Malayan Shores. Muwu Shosa, Singapore.225 pp., plates
1-112.
- Barnes, Robert
D. & Ruppert, Edward E., 1996. Invertebrate Zoology. Harcourt
College Publishers. 6th Edition. pp. 1056, G-1-16, I-1-30.
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